1. Field of the Invention
The present invention relates generally to a switch mechanism for key-entry operation and, more particularly, to a key-entry switch (hereinafter referred to as a key switch) preferably used for a keyboard incorporated as an input device in electronic equipment. The present invention also relates to a keyboard provided with a plurality of key switches.
2. Description of the Related Art
In the technical field of portable electronic equipment such as notebook-size personal computers or wordprocessors, etc., various techniques have been proposed to facilitate a reduction in height or thickness of the housing of equipment including a keyboard and to improve the portability of the equipment. Particularly, when the height of a keyboard provided with a plurality of key switches is to be reduced, it has been generally required to maintain the stroke of each key switch at a predetermined length to ensure constant operational properties thereof and, simultaneously, to reduce the entire height of the key switch upon both the non-operated (or switched-off) and operated (or pushed-down and switched-on) conditions thereof.
A conventional key switch for use in a relatively thin keyboard with a reduced height generally includes a base, a key top disposed above the base, a pair of link members for supporting the key top above the base and directing the key top in the vertical or up-and-down direction, and a switching mechanism for selectively opening/closing contact points in an electric circuit in accordance with the vertical or up-and-down movement of the key top. The conventional pair of link members has been provided essentially with any one of three types of configurations.
First type pair of link members may be referred to as a gear-link type, wherein the link members are assembled together into a reverse V-shape as seen in a lateral direction and meshed at toothed end regions thereof with each other, each link member being slidably engaged at a first end region thereof with the base and pivotably engaged at the toothed or second end region with the key top (see, e.g., Japanese Unexamined Patent Publication (Kokai) No. 11-3628). Second type pair of link members may be referred to as a pantograph type, wherein the link members are assembled together into an X-shape as seen in a lateral direction and rotatably joined at intersections thereof with each other, each link member being slidably engaged at a first end region thereof with one of the base and the key top and pivotably engaged at a second end region with the other of the base or the key top (see, e.g., Japanese Unexamined Utility Model Publication (Kokai) No. 5-66832). Third type pair of link members may be referred to as a modified pantograph type, wherein the link members are assembled together into an X-shape as seen in a lateral direction and slidably connected at intersections thereof with each other, each link member being slidably engaged at a first end region thereof with the base and pivotably engaged at a second end region with the key top (see, e.g., Japanese Unexamined Patent Publication (Kokai) No. 9-27235).
In the conventional key switch having any one of the above types of link members, the link members are shifted in a mutually interlocked manner, and the key top is thereby allowed to be moved in a parallel displacement in a substantially vertical direction relative to the base, while keeping a predetermined posture of the key top. Once the key top reaches a lowermost position of a vertical or key-entry stroke thereof, the link members are laid in a generally horizontal position under the key top and received inside an opening defined in the base. This arrangement permits the entire height of the key switch to be reduced in both the non-operated and operated conditions while maintaining the key-entry stroke of the key top at a desired length.
In the conventional key switch having the gear-link type pair of link members as described, each link member includes a pair of arms extending generally parallel to each other and a pair of axles formed at the second end region of the link member, i.e., the distal end region of the respective arms, the axles extending outward along the rotation axis of the second end region for pivotable engagement with the key top. Each arm of the link member is further provided with one or more teeth projecting outward from the second end region in a direction generally orthogonal to the rotation axis, the teeth constituting an interlocking element for meshable engagement with the second end region of the counterpart link member.
On the other hand, the key top is provided with two pairs of pivot supports for pivotably supporting the axles of the respective arms of the respective link members. The pivot supports are formed on the inner surface of the key top as separate plate-like projections extending generally parallel to one another. Each pivot support includes a bearing hole for pivotably receiving the axle of each arm of each link member and a slit communicating with the bearing hole. The slit of the pivot support is shaped and dimensioned so as to define an opening smaller than the associated axle of the link member. The slits of four pivot supports extend generally parallel to one another and in a direction generally perpendicular to the inner surface of the key top.
In the assembling process of the abovedescribed key switch, first the link members are arranged so as to engage the first end regions thereof to the base and to mesh the corresponding teeth thereof with each other, and are laid in a generally horizontal position to be received inside the opening of the base. In this state, the link members are positioned at a location substantially identical to a location defined by the lowermost position of key-entry stroke of the key top. Then, the key top is put on the link members so as to bring the respective pivot supports into contact with the associated axles, and is pushed down on the link members. Thereby, the axles are inserted into the slits of the correlate pivot supports under pressure to elastically deform the pivot supports, and are finally press-fitted into the bearing holes in a snap-fit manner. This configuration generally facilitates both the assembling process of the key switch and the construction of a mold used for molding the key top.
In the above conventional structure of the key switch having the gear-link type pair of link members, the base and the link members are typically shaped and dimensioned so that a slight clearance may be defined between the second end region (especially, the distal end of each axle) of each link member and the inner peripheral surface at the opening of the base after the assembling process is completed, so as to ensure the relatively easy press-fitting operation in the assembling process for the respective pivot supports of the key top fitted with the associated axles of the link members. However, such a clearance tends to enable the link members located inside the base opening to be slightly displaced in a horizontal direction, which may result in an incorrect intermesh between the toothed end regions or interlocking elements of the link members located inside the base opening due to an inadvertent mutual horizontal displacement caused between the link members before the key top is fitted to the link members.
If the key top is press-fitted to the incorrectly intermeshed link members as described, problems may arise wherein the tooth or teeth of the toothed end regions of the link members are deformed or damaged, which may affect the key-entry operation or stroke properties of the key switch. Accordingly, it is typically required for the assembling process of the conventional key switch to correct the intermeshed state of the gear-link type pair of link members before the key top is fitted with the link members.
In a typical assembling process of a conventional keyboard including a plurality of key switches having the above-described structure, a large-sized base panel (referred to as, e.g., a switch panel) with a plurality of openings respectively used for the individual key switches is provided, and the plural pairs of link members are inserted into the respective openings in the intermeshed state as described and, in this state, the key tops of the individual key switches are press-fitted to the associated pairs of link members. Therefore, it is necessary to investigate the intermeshed state of the link members of all the key switches and properly correct the probable incorrectly intermeshed state thereof, before the key tops are fitted to the link members. However, such investigation and correction have generally been performed by a manual operation, and thus have required much time and the skill of an operator, which may increase the manufacturing cost of the key switches as well as of the keyboard. Also, a certain careless error in correction may arise when the investigation and correction are repeatedly performed in the assembling process of many keyboards.
Also, in a conventional key switch having any type pair of link members, i.e., the gear-link type pair, the pantograph type pair or the modified pantograph type pair, each link member is pivotably connected through the axles provided on the first or second end region of the link member with either the base or the key top. The axles of each link member are respectively fitted into the bearing holes or grooves of the associated pivot supports provided on the base or the key top. In this structure, the slit communicating with the bearing hole is typically formed in each pivot support so as to ease the press-fitting operation of the axle and simplify the construction of a mold for the key top, as already described. However, the slit may facilitate the generation of backlash of the axle in the bearing hole, which may cause problems of the fluctuation or wobble of the key top and the resultant noise during the key-entry operation. If the pivotable engagement between the axle and the bearing hole is designed to be excessively tight to solve the above problems, the key-entry operation properties may be deteriorated.
Moreover, in the conventional key switch having any type pair of link members, i.e., the gear-link type pair, the pantograph type pair or the modified pantograph type pair, the key top is continuously applied with a biasing force by an elastic member in a vertical upward direction away from the base. In the key-entry operation, the key top is pushed downward against the upward biasing force of the elastic member, whereby the electric contact points of the switching mechanism disposed beneath the key top are closed. Therefore, when a downward pushing force to the key top is released, the key top is moved back to an initial or uppermost position in the key-entry stroke by the biasing force of the elastic member under the guiding action of the link member pair. In this respect, the uppermost position of the key top is determined at the instant when the axles provided to project from the slidable end region of each link member are abutted to and stopped by the walls of the associated slide supports, slidably supporting these axles, formed on the base or the key top. Consequently, at the time when the key top reaches the uppermost position, a collision noise is generated between the axles on the slidable end region of each link member and the walls of the associated slide supports on the base or the key top. It is desired to reduce this type of collision noise generated between some components in the key switch as much as possible, in consideration of the use of the keyboard in situations demanding quietness.
Incidentally, in the assembling process of the conventional keyboard, the key top of each key switch is often printed with desired one or more signs, such as letters or symbols, after the key tops of all the key switches are fitted to the associated link member pairs. In the case where the key switches incorporated in the keyboard include the key tops having various shapes and/or colors, it is necessary to manage the stock of the various types of precursor or non-printed key tops according to the shapes and/or colors thereof, preparing for the assembling process of the keyboard, and to supply the precursor key tops to assembling lines while identifying the required shapes and/or colors thereof. Moreover, in the case where the key tops formed from various materials should be stored, for the purpose of, e.g., allowing respective key tops to be subjected to different printing steps such as laser printing, pad printing, and so on, it is necessary to manage the stock of the precursor key tops according to the materials thereof in addition to the shapes and/or colors. However, it is ordinarily difficult to visually identify the key tops having different materials but identical shapes and colors. If the key tops having different materials but identical shapes and colors are accidentally or carelessly mixed in a storage and/or supply stage, the assembling process of the keyboard may suffer due to, e.g., a poor printing step wherein the key top made of a material suitable for pad printing is subjected to laser printing.
It is therefore an object of the present invention to provide a key switch including a key top adaptable for a key-entry operation, in which, in an assembling process, a gear-link type pair of link members can be relatively easily set in an accurate intermeshed state and the possibility of inaccurate intermeshing can be reduced or eliminated, before the key top is fitted with the link members, so that the assembling process of the key switch and of a keyboard can be simplified and the manufacturing cost thereof can be reduced.
It is another object of the present invention to provide a key switch including a key top adaptable for a key-entry operation, in which the backlash in a pair of link members generated due to a clearance defined between certain components constituting pivotable joints of the link members to a base or the key top can be restrained, without deteriorating key-entry operation properties, so that the fluctuation or wobble of the key top and the resultant noise, which may be generated during the key-entry operation, can be reduced or eliminated.
It is yet another object of the present invention to provide a key switch including a key top adaptable for a key-entry operation, in which, in the key-entry operation of the key top, a collision noise, generated between certain components at the instant when the key top reaches an initial uppermost position in a key-entry stroke, can be reduced or eliminated.
It is a further object of the present invention to provide a key switch including a key top adaptable for a key-entry operation, which can make it possible to precisely and relatively easily identify various key tops made of different materials, so that the productivity of a keyboard incorporating therein a plurality of key switches can be improved.
It is an yet further object of the present invention to provide a keyboard incorporating therein a plurality of key switches, which can provide good assembling properties and superior operability of key switches.
In accordance with the present invention, there is provided a key switch comprising a base; a key top arranged above the base; a pair of link members interlocked with each other to support the key top above the base and direct the key top in a vertical direction, each of the link members including an engagable region engaged with the key top; and a switching mechanism capable of opening and closing an electric circuit in connection with a vertical movement of the key top; wherein the base is provided with an inner peripheral surface defining an opening capable of receiving the pair of link members, and a protruding wall part provided on the inner peripheral surface to locally reduce a clearance defined between the inner peripheral surface and the engagable region of each of the link members when the link members are received in the opening.
In one aspect of the invention, each of the link members may be provided at the engagable region with an axle projecting outward, the axle being pivotably connected with the key top, and the base may be provided with a plurality of protruding wall parts on the inner peripheral surface, each of the protruding wall parts being positioned so as to oppositely and closely face the axle of each link member when the key top is located at a lowermost position of a key-entry stroke.
In this arrangement, each of the protruding wall parts may have a cross-sectional shape smaller than that of the axle of associated one of the link members.
It is preferred that the protruding wall part has a uniform height measured from the inner peripheral surface.
It is also preferred that the protruding wall part has a gradually increased height measured from the inner peripheral surface as seen in a direction away from the key top.
The present invention also provides a key switch comprising: a base; a key top arranged above the base; a pair of link members interlocked to each other to support the key top above the base and direct the key top in a vertical direction, each of the link members including an engagable region engaged with one of the base and the key top; and a switching mechanism capable of opening and closing an electric circuit in connection with a vertical movement of the key top; wherein each of the link members is locally abutted in the engagable region onto one of the base and the key top under an elastic restoring force generated relatively in each link member and the base or the key top with which the link member is engaged.
In one aspect of the invention, the key top may be provided with pivot supports and abutting plates arranged respectively adjacent to the pivot supports, each of the link members may be provided at the engagable region with an axle projecting outward, the axle being pivotably connected with one of the pivot supports of the key top, and the axle may be provided with an end surface including an apex abutted to one of the abutting plates arranged adjacent to one of the pivot supports with which the axle is pivotably connected.
In this arrangement, the axle may be abutted at the apex to one of the abutting plates under a certain pressure caused due to an elastic restoring force generated relatively in one of the link members and an associated one of the abutting plates.
In another aspect of the invention, the base may be provided with slide supports, each of the link members may be provided at the engagable region with an axle projecting outward, the axle being slidably connected with one of the slide supports of the base, and the axle may be provided with an end surface including an apex abutted to one of the slide supports with which the axle is slidably connected.
In a yet another aspect of the invention, the base may be provided with slide supports, each of the link members may be provided at the engagable region with an axle projecting outward, the axle being slidably connected with one of the slide supports of the base, and the axle may be provided with an annular rib circumferentially extending along a part of an axial length of the axle, the annular rib being abutted to one of the slide supports with which the axle is slidably connected.
In a further aspect of the invention, the key top may be provided with pivot supports, each of the link members may be provided at the engagable region with an axle projecting outward, the axle being pivotably connected with one of the pivot supports of the key top, and each of the link members may be provided with a textured surface located around a proximal end of the axle, the textured surface being abutted to one of the pivot supports with which the axle is pivotably connected.
In a yet further aspect of the invention, the key top may be provided with pivot supports, each of the link members may be provided at the engagable region with an axle projecting outward, the axle being pivotably connected with one of the pivot supports of the key top, and each of the link members may be provided with a protuberance located adjacent to a proximal end of the axle, the protuberance being abutted to one of the pivot supports with which the axle is pivotably connected.
The present invention also provides a key switch comprising a base; a key top arranged above the base; a pair of link members interlocked to each other to support the key top above the base and direct the key top in a vertical direction, each of the link members including an engagable region slidably engaged with one of the base and the key top; a switching mechanism capable of opening and closing an electric circuit in connection with a vertical movement of the key top; and a buffering portion for gradually braking a sliding motion of the engagable region of each of the link members relative to one of the base and the key top caused in accordance with the vertical movement of the key top just before the key top reaches an uppermost position of a key-entry stroke.
In one aspect of the invention, the buffering portion may comprise a buffer plate extending from the base, the buffer plate being elastically deflected by one of the link members colliding with the buffer plate just before the key top reaches the uppermost position.
In another aspect of the invention, the buffering portion may comprise a slanted wall surface formed on the base to face the engagable region of one of the link members, the slanted wall surface exerting a contact pressure against one of the link members colliding with the slanted wall surface just before the key top reaches the uppermost position.
In a further aspect of the invention, the key switch may further comprise a sheet member arranged beneath the base, and the buffering portion may comprise a high-friction area formed on the sheet member, the high-friction area exerting a friction force against one of the link members running onto the high-friction area just before the key top reaches the uppermost position.
The present invention also provides a key switch comprising a key top having an operating surface for a key-entry operation and supported to be directed in a vertical direction above a base; the key top being provided with an identifying portion for identification of an attribute of the key top.
In one aspect of the invention, the identifying portion may comprise a plurality of elements having various features including at least one of numbers, locations, shapes and dimensions.
In this arrangement, the key top may further include a brim surface adjacent to the operating surface, and the elements may be formed as recesses on the brim surface.
The present invention also provides a keyboard comprising a plurality of key switches, each of the key switches having any one of the above-described features.